update preprocess data

model_zoo/official/cv/ssd/src/dataset.py

@@ -233,6 +233,7 @@ def create_voc_label(is_training):
                      'id': img_id}
             json_dict['images'].append(image)
 
+    if not is_training:
         for cls_name, cid in cls_map.items():
             cat = {'supercategory': 'none', 'id': cid, 'name': cls_name}
             json_dict['categories'].append(cat)